The present invention relates to a image read-out device and, more particularly, to a two-dimensional image read-out sensor device which includes sensor elements disposed over two dimensions.
The MOS image sensor, CCD image sensor, close-contact type image sensor, etc. have been developed for an image reading device in, for example, a facsimile machine, an intelligent copier, etc. To read two-dimensional image information, the two-dimensional image information is converted into electric signals by mechanically scanning the one-dimensional image sensor such as the MOS image sensor and the CCD image sensor, in the two-dimensional directions.
Both of the MOS image sensor and the CCD image sensor are formed on a monocrystal semiconductor substrate through the use of the IC (Integrated Circuit) technique. Thus, a large size sensor is difficult to form. Accordingly, the MOS image sensor and the CCD image sensor are generally combined with an optical lens system so as to form a demagnified image on the image sensor elements. The optical lens system requires a predetermined optical path which prevents the reduction of the size of the image reading apparatus.
To solve the optical path problem, the close-contact type image sensor has been proposed, which includes a light responsive member having a size greater than or equal to the original document size. The image of the same size as the original document is formed on the light responsive member via an optical fiber. The contact type image sensor needs the light responsive member having the same size as the original document and, therefore, a uniform photoconductive layer of a considerably large size must be formed.
The close-contact type image sensor employing a photoconductive layer made of CdS-CdSe mixture crystal, amorphous Se, Se compound, amorphous Si or the like has been proposed. However, this type of the image sensor has a complicated construction which needs a complicated manufacturing process therefor. Furthermore, the reading speed is limited by the response speed of the photoconductive layer.
If such a one-dimensional image sensor is used to read two-dimensional image information, the reading speed is considerably slow because the same photoconductive sensor portion of the one-dimensional sensor must be repeatedly scanned on the original document. Moreover, it is difficult to integrally connect the photoconductive sensor portions with switching elements through the use of the IC technique. To connect the photoconductive sensor portions with the switching elements, the switching elements and the photoconductive sensor portions are connected each other on a same substrate by bonding. However, as the number of photoconductive sensor portions is increased for the improvement of the image resolution, the numbers of switching elements (or ICx) is increased, so that a driving circuit has been complicated and the image sensor becomes expensive.
However, no terminal connection suitable for the two-dimensional image read-out sensor device has been proposed. Therefore, the conventional two-dmensional image sensor device has a large and complicated construction and must be driven by a driving circuit having a great number of the switching elements (or ICs).